1. Field of the Invention
The present invention relates in general to a pedestrian protection apparatus for a vehicle, and in particular to an improved structure of the pedestrian protection apparatus disposed at a lower part of a front face of the vehicle and arranged to sweep a lower part of a leg portion of a pedestrian by contact with the lower part of the leg portion of the pedestrian that has collided with or contacted the front face of the vehicle, thereby protecting the leg portion of the pedestrian.
2. Discussion of Related Art
In vehicles such as automotive vehicles, there are conventionally disposed, at a front face, a rear face, or side faces, of the vehicles, various types of protection apparatus which absorb an impact energy generated upon a collision for thereby protecting a vehicle body and vehicle passengers. In recent years, there is disposed, at the front face of the vehicle, an apparatus for protecting a pedestrian upon collision or contact of the pedestrian with the front face of the vehicle.
As one type of the pedestrian protection apparatus, there is known a so-called leg-sweep apparatus which is disposed inside of a front bumper or disposed at a lower part of the front bumper independently of the front bumper. The leg-sweep apparatus is arranged to apply, to a lower part of a leg portion of the pedestrian, a counterforce with respect to an impact load that is inputted upon collision of the pedestrian with the front face of the vehicle and sweep (scoop up) the lower part of the leg portion of the pedestrian, thereby causing the pedestrian to fall down or to be thrown over toward the vehicle. Thus, it is possible to minimize occurrence of injuries to the leg portion of the pedestrian such as bone fractures, thereby assuring protection and safety of the pedestrian.
Examples of the leg-sweep apparatus as one type of the pedestrian protection apparatus are disclosed in a patent publication document 1 (JP-A-2001-277963), a patent publication document 2 (JP-A-2004-25976), and a patent publication document 3 (JP-A-2004-203183), for instance. The pedestrian protection apparatus disclosed in the patent publication document 1 is arranged to be disposed at the lower part of the front of the vehicle and includes: a resin foam body which extends in a vehicle width direction and at least a part of which protrudes from the front face of the vehicle; and a beam member which extends in the vehicle width direction while being in contact with the back surface of the resin foam body. The pedestrian protection apparatus disclosed in the patent publication document 2 is formed of a metal pipe or the like and is fixed to the lower part of the front face of the vehicle so as to extend in the vehicle width direction. The pedestrian protection apparatus disclosed in the patent publication document 3 includes: a plate member located so as to extend in a frontward and backward of the vehicle and fixed to the lower part of the front of the vehicle; and a plurality of flat ribs disposed on a front portion of the plate member so as to extend upright therefrom, so that the front portion of the plate member has an increased rigidity. Further, a rear portion of the plate member has a flat plate-like configuration extending in the frontward and backward direction of the vehicle. The thus constructed apparatus is fixed to the vehicle at a rear-side end section of the rear portion of the plate member. However, the pedestrian protection apparatus disclosed in those documents have drawbacks which should be rectified.
The pedestrian protection apparatus disclosed in the patent publication document 1 needs a large number of components, inevitably pushing up the cost of the components. Further, it is cumbersome to install the apparatus on the vehicle. The pedestrian protection apparatus disclosed in the patent publication document 2 inevitably has a large weight. Further, it is difficult to form the apparatus to have a configuration corresponding to that of the front face of the vehicle.
The pedestrian protection apparatus disclosed in the patent publication document 3 ensures a sufficiently reduced weight where the plate member and the plurality of ribs are formed integrally with each other using a synthetic resin material, for instance. Moreover, the apparatus advantageously achieves excellent formability and a reduction in the number of components by employing, in formation of the plate member and the plurality of ribs, a molding technique using metal dies such as injection molding. Thus, the drawbacks experienced in the pedestrian protection apparatus disclosed in the patent publication documents 1 and 2 are eliminated in the apparatus disclosed in the patent publication document 3. The apparatus disclosed in the patent publication document 3, however, suffers from some obstacles to improvement in impact performance described below.
Namely, the pedestrian protection apparatus disclosed in the patent publication document 3 enables, upon contact with the leg portion of the pedestrian, the impact load in the load characteristics to rise promptly and reach a target value quickly, thus ensuring excellent impact performance that permits a sufficient high degree of counterforce with respect to the impact load to be instantaneously exhibited. To this end, the height of each of the ribs provided on the front portion of the plate member needs to be increased to give sufficient rigidity to the front portion of the plate member to which the impact load is inputted for thereby preventing the front portion from being easily deformed. The increase in the height of each rib, however, increases the weight of the pedestrian protection apparatus as a whole even when the apparatus is constituted by a resin-molded product. In this instance, the merit of the resin-molded product, i.e., lightness, is considerably deteriorated. Further, where the height of each rib is increased, it is required that metal molds to be used in molding be formed with a recessed portion having a large depth for forming each rib. In this instance, it takes additional time to manufacture the metal mold. Moreover, the mold release characteristics may be deteriorated. In consequence, there may be caused a problem of deterioration in manufacturing efficiency of the pedestrian protection apparatus as a whole.
Under the situations mentioned above, a patent publication document 4 (JP-A-2002-264741) discloses a pedestrian protection apparatus in which reinforcing beads are formed integrally on the front portion of the plate member in place of the flat plate-like ribs. Each reinforcing rib includes: an extending portion which extends in a frontward and backward direction of the vehicle with a channel-like configuration that is open downward; and a plate-like end portion which extends integrally from a rear-side edge of the extending portion for connecting the rear-side edge of the extending portion and the rear portion of the plate member. The thus constructed pedestrian protection apparatus ensures the same degree of rigidity at the front portion of the plate member as that ensured when the flat plate-like ribs with a large height are formed integrally on the front portion of the plate member, while keeping the depth or the height of each reinforcing bead relatively small. Accordingly, the pedestrian protection apparatus disclosed in the patent publication document 4 eliminates not only the above-mentioned drawbacks experienced in the pedestrian protection apparatus disclosed in the patent publication documents 1, 2, but also the above-mentioned problem experienced in the pedestrian protection apparatus disclosed in the patent publication document 3.
The inventors of the present invention conducted various experiments and studied the pedestrian protection apparatus disclosed in the patent publication document 4. As a result of the study, it was found that the apparatus had the following drawbacks.
Namely, in the pedestrian protection apparatus disclosed in the patent publication document 4, a connecting portion between the end portion of each reinforcing bead and the rear portion of the plate member is formed as an angular folded or bent portion, so that stress is applied to such folded portion upon inputting of the impact, resulting in comparatively easy flexing deformation of the plate member at a boundary between its front and rear portions at which such folded portion is located. In consequence, there may be caused a delay in rise of the impact load in the load characteristics, rendering it difficult for the impact load to instantaneously reach the target value. Thus, the pedestrian protection apparatus disclosed in the patent publication document 4 does not ensure satisfactory impact performance that permits a sufficiently high degree of counterforce with respect to the impact load to be instantaneously exhibited.
In the pedestrian protection apparatus disclosed in the patent publication document 4, because the connecting portion between the end portion of each reinforcing bead and the rear portion of the plate member is formed as the angular folded portion as described above, the inner (anterior) surface of the end portion assumes a flat plane configuration. Accordingly, during running of a vehicle on which the apparatus is mounted, a portion of the air flow flowing through the lower part of the vehicle in the backward direction, which portion of the air has entered the inside of the reinforcing bead, is brought into hard contact with the inner (anterior) surface of the end portion having the flat plane configuration, thereby causing a large air resistance that may lead to a deterioration in the aerodynamic characteristics of the pedestrian protection apparatus and accordingly of the vehicle.
The inventors of the present invention conceived of providing flat plate-like auxiliary ribs each extending continuously in the frontward and backward direction over the end portion of each reinforcing bead and the front-side end section of the rear portion of the plate member, in an attempt to increase the strength of the plate member with respect to deformation (deformation strength) at its boundary portion between the front and rear portions where the connecting portion (folded potion) between the end portion of each reinforcing bead and the rear portion of the plate member is located.
The inventors have conducted a known collision test using the pedestrian protection apparatus having such auxiliary ribs. The result of the collision test indicated the following: Although the boundary portion between the front and rear portions of the plate member is prevented from being deformed, stress concentrates, upon inputting of the impact load, on two locations at which a front end and a rear end of each auxiliary rib are located because the connecting portion of each auxiliary rib with the plate member has a linear configuration. In this instance, the plate member tends to be easily subjected to flexing deformation at portions thereof corresponding to the above-indicated two locations at which the front and rear ends of each auxiliary rib are respectively located, thus rendering it difficult for the pedestrian protection apparatus to ensure the desired impact performance as described above.